This is not Trapania maculata. Trapania maculata has no oral papillae around the front of the head, it has long extra-rhinophoral processes, and its extra-branchial processes are much longer than those on any of these animals.

This dorid nudibranch is characterised by possessing some gold markings (either lines, or dashes, or spots) on the mantle, and by 4 tentaculate processes off the front of the head. By contrast, the similar looking Polycera faeroensis is characterised by the complete absence of gold markings on the mantle, and by 8 tentaculate processes off the front of the head.

This is a colour variation of common North Atlantic species Polycera quadrilineata (Müller, 1776). It is an interesting case when some colour morphs of one species (e.g. Polycera quadrilineata) may approach colour variants of another species of the same genus (e.g. Polycera atra), significantly differs in other features.